Process for the manufacture of articles in silica glass



Dec. 28 1926.

H. GEORGE PROCESS FOR THE MANUFACTURE OF ARTICLES IN SILICA GLASS Filed July 15, 1924 Patented 28 1926. i a h UNITED STATES PATENT OFFICE.

' nnnnrononomor rams, rnaiieiijassrenoaro socin'rn momma ARTZ SILICE, or rams, FRANCE, A conrorwnon or raancn.

rnocnssron THE MANUFACTURE or enric es m'srmca GLASS. a l cationfiled July 15, 1924, Serial n 726,141.51! in France November2, 1923.

The present invention has for its object manufacture of an article of more complia process of manufacture of articles'of vacated shape, and p rious shapes in fused pure silica. 3 r Figure is a corresponding view of a In the present state of the technics of device intended for the-shaping of articles silica glass, the operation is carried out in of fused silica. v 50 the following manner: i In the arrangement represented in Figure The raw material, for example sand or 1, forthe manufacture of an ingot closed rock crystal is heaped around a graphite at its lower end, the mould a is a rod of electrode. -.This electrode being raised by graphite or amorphous carbongthe charge 1) ithe passage of the current to a high. temis co 'tuted by sand .or rock crystal suit- 65. I

pera'ture, the sand melts around the elecably powdered or by any other raw material 1 trode'and there is obtained finally a tube possessing more than 99.5 per cent of silica;

with thick' walls known as thein'got... This this charge is contained ina vessel 0 which ingot is then expanded in a mould. This may beof porcelain, micanite, fused silica 1 method of procedure presents the -follow-i or any other insulating material. -The 70 'ing disadvantages: mould a is buried in the charge at-its lower (1) It is impossible to obtain articles with end;

thicknesses varyinggreatly in their difi'er- Around the vessel cthere is arranged a ent parts. helicoidal winding d consisting of a copper (2) The ingot being open 'at its lowerend, Or-aluminum tuhe:traversed by an alternat- 7 i of any shape. glazed either externally or in-, may be cooled y watercirculation; r 8

closed articles-(for example balloons) can ing c'urreht of ,ver high frequency (40,000 be obtained only by welding the bottom of. periods persecon for example), produced the ingot by compression before moulding, by known means (high frequency alternator, which then constitutes a weak point in the. electrode or spark'generator, or three-elecu I 5 article. V 1 trode lamps), -The winding of the t-ubed B (3) Thearticles are only completely vitri-. upon the insulating wall cis effected in such fied' (glazed) on the interior. away as to produce the maximum-field com- The process forming the subject of the patible with the. tension-between thecoils present invention allows of obtaining articles and the intensit of the current. The tube ternally, and ingots or articles closed at In these conditions'theinould-a is carried one end or at both ends. very rapidly. to anextremely high tempera- It consists in melting the raw material 'ture and the charge-melts regularly at its in actual contact with the mould of refracv contact. The operation is stopped when the tory and conducting material, preferably article attains the desired thickness. The 00 graphite or'amorphous carbon, the charge ingot obtained is shown'in the drawing'in of very-high frequency.

being heaped according to thecircumstances, dotted lines at e. If it is desired then to within the mould or upon its outer surface. mould this ingot to another shape, it is only The mould is raised to the temperature, alnecessary to-withdraw the rod. (1 smartly and 40 lowing the chargeto melt at its contact, by to expand the ingot in a suitable mould. 05

currents ofhigh intensity developed by in'- In order to-obtain by this proc'ess a solid duction within its mass by a magnetic field body closed at the two ends, it sufiices-toi sink the'mould completely in the charge.

The accompanying sheet of drawings rep Figure 2 thus "represent a mould a ini resents byway of exampl s d-ifi r nt for tended for the fabrication ofcrucibles: The 100 Figure2 is a corresponding "v1 in whichtheinvention may be carried out. i o n d 6? is Shown in dotted Figure 1 is a view in axial section through hi pa t, ut i w t t e p e i w, 111

a "device for .thefmanufacture of an ingot yield two silica crucibles and free the mould 1 closed at itslow-er end. 7 for afurther melting. 7

'ew for th In order to obtain an; article glazed 011.105 manufacture of crucibles. the exterior. the mould a (Figure 3) will Figure 3 is acorresponding view for the hav a tu ular shap a d the charge I). will manufacture .of an article'glazed on the ex be heaped in the interior. I terior. Y Externally of the mould, betweenthe lat- 5 Figure 4 is a co responding view for the tci' and the vessel 0, there is arranged a suititble heat repeller f (wood-charcoal, lamp black,-'etc.)

Inorder to obtain more complicated ar-' ticles, it is evident that the mould can be arranged in several parts for facilitating the Withdrawal and can comprisecores if desired. Figure 4 represents tlief-n'iould a of a silicia insulator. Moreover,i'the mould for current operations can bereplaced by a simple crucible.

To this crucible can be adapted any suitable devices for allowing the shaping, drawin or moulding of the fused charge.

bus the device of Figure 5 allows of moulding a piece of fused silica to the desired shape.

This device is particularly suited for the softening of articles of transparent silica for optical work, with a View to giving them an almost final shape before cutting.

The mould is in several parts; it comprises one part a, with a hollow of a shape corresponding to one face of the lens or other article to be obtained, and a piston a with fused silica without bubbles by starting from rock crystal granules. The operation can equally pure silica and which by their silica; it is evident that without in any way changin the invention, the charge might heformed by a mixture very rich in silica, in order to obtain for example special. glasses having a content of silica exceeding 90 per cent, glasses of which the melting temperatures approach those employed for properties are close to this last product.

What I claim is: r

1. A process for the manufacture of articles of various shapesjn silica glass, consisting in melting the charge in actual contact with a mould, of refractory and conducting material, .raised to high temperature by high frequency induction.

2. A process for the manufacture of articles of various shapes in silica lass, consisting in melting a charge of silicious material in actual contact with a mould of refractory and electrically conducting material, entirely embedded within the charge to be melted, and insulated from any source of heat and from any metallic connection, by raising the temperature of said mould, and of the charge, by high frequency induction. Y

In testimony whereof, I have signed my name to this specification at Paris, France.

HENRI GEORGE. 

